Two-cycle engine



J. KNIGHT.

TWO CYCLE ENGINE.

APPLICATION FILED NOV.19,1918.

Patented Mar. 23, 1920.

' JOSEPH KNIGHT, OF LIVERPOOL, ENGLAND.

TWO-CYCLE ENGINE.

Specification of Letters Ilatent. Patented Man 23, 1920 Application filed November 19, 1918. Serial No. 268,177.

To all whom it may concern:

Be it known that I, JOSEPH KNIGHT, a subject of the King of Great Britain, and a resident of, Aintree, Liverpool, England, have invented a new Two-Cycle Engine, of which the following is a specification.

This invention relates to internal combustion engines of the two stroke cycle and of that type in which two piston elements reciprocate in opposite directions and are coupled up to a common crank shaft. The object of the present invention is to provide an engine of this type such that a greater efliciency in power may be obtained for the same consumption of fuel over existing engines, by timing the explosion so that a maximum of the elfort is developed as a true twisting action on the-crank shaftand s0 avoid the wasteful stresses set up on the shaft, bearings, crank and connecting rod when the explosion takes place at or near the dead center.

According to this invention. the explosion is timed to take place when one crank has moved 35 to 45 degrees from the dead center, and in order that this initial preexplosion movement of the crank shall .not result in a loss of compression due to the corresponding movement of the piston, the effective space :behind the piston proper in which the maximum compression has been set up is maintained constant, or may even be reduced to increase the compression, by

providing that the piston is followed up from the dead center position to that at whichthe explosion takes 'place, by a secondary piston coupled to the same crank shaft as the primary piston. For instance this action may be effected by arranging the primary piston to work within a secondary sleeve .piston having a closed end and slidable in the fixed outer cylinder of any suitable construction, and coupling the primary or piston proper and the sleeve up to cranks set, at 135 to 145 apart.

Where the efi'ective space in which the compression has been set up is subsequently reduced the supercompression thus set up may be utilized to effect spontaneous fir ing of the combustible mixture by the heat generated. In other types of engines where spontaneous firing has been attempted backfiring has been liable to occur, but with anarrangement of engine in accordance-with this invention any possibility of the direction of rotation being reversed 1s avolded.

A further feature of the invention relates to means whereby an adequate volume ofcombustible mixture may be pumped into the working space between the piston elements. This may be efl'ected by arrangin one piston element to work within anot er sleeve piston, which reciprocates in an outer cylinder and by forming the sleeve iston with an enlarged head so that the v0 ume swept out by the sleeve piston in the external cylinder 1n pumping the charge to the working space may. be equal to or greater than that contained between the piston elements when they are fully apart. The engine in this preferred form is constructed after the manner of a known type of internal combustion engine having an inner piston sliding within a secondary sleeve plston within which the charge is fired, the pistons working in opposite directions and being coupled up to a common crank shaft.

An engine constructed in accordance with this invention is shown in the accompanying drawings, in which Figure 1, is a medial vertical section through one cylinder of the engine, andFig. 2, is a side view in elevation of the engine showing a two cylinder arrangement. a

In carrying out the invention the engine comprises a primary or piston proper 1 reciprocating Within a secondary sleeve piston 2 which works within a fixed outer cylinder 3 of any suitable construction, the primary piston and sleeve piston being coupled up by their respective connecting rods l and 5 to cranks ('3 and 7 set relatively apart at an angle of 145 degrees as shown, the sleeve piston 2 being provided with twin connecting rods 5. The explosive mixture is trapped in the space between the piston proper 1 and the closed end of the sleeve piston 2 and reaches its maximum compression when the piston crank 6 is at the inner dead center and the sleeve crank in advance by 145. Firing is arranged not to take place until the piston crank has moved a considerable angle from the dead center, say 35? to 45, but compression is not lost during the corresponding movement of the piston proper 1 by reason of the fact that the sleeve piston 2 partakes of a compensating movement in the same direction in the outer cylinder 3, thus maintaining the compression space between the pistons constant, while by making the sleeve crank By this means the maximum effort of the explosion is expended on the crank 6 only when it can develop the greatest torque on the shaft, a twisting couple being obtained to the outlet 1?.

piston acts as a self-contained pump in the compressing the com-.

cylinder 3 fitting over the head 8 by the reversed pull set up by the sleeve piston 2 on its connecting rods 5 and cranks 7 which are then past the lower or outer dead center. The exhaust being timed to open at about the same period of the stroke as that obtainingin existing engines, 1t follows that the intense heat of the explosion is in contact with the engine surfaces for a lesser period than normally obtaining, where the explosion takes place at about the inner dead center, and consequently the deleterious effect on the metals is correspondingly reduced.

Where the engine comprises a piston 1 working within a sleeve piston 2 as described, the outer cylinder 3 is provided with spring controlled inlet valves 8 ada ted to act as suction inlets for the combusti le mixture to the head of the outer cylinder 3 on the downward or outward movement of the sleeve piston 2, a charge being thus drawn into the space 9 between the sleeve piston' end and the outer cylinder, which charge is compressed on the next upward or inward movement of the sleeve piston 2, and admitted through a spring controlled valve 10 or a number of such valves in the end of thesleeve piston tothe firing space 11 in the interior of the sleeve piston, the charge bein thus primarily compressed in the space 9%)efore admittance to the firing space 11 and effectively sweeping out the spent gases therefrom through exhaust ports 12 in the sleeve of any suitable disposition uncovered by the outward movement of the piston proper 1, when these ports register with ports 12 in the fixed In this way the sleeve engine for primarily bustible mixture.

The spring controlled inlet valves 8 are fitted into the head 8 by means of screwed and the head 8 is outer cylinder 3, a cap 15 spigoted into the and being held in position by a nut 16. This cap 15 forms with the head 8 an annular chamber to which is led the fuel charge from the carbureter by way of the inlet 15". The inlet valve 10 in the end of the sleeve piston I 2. is carried on a detachable bush 17 the seat of which is perforated at 18 to provide passages for the combustible mixture. The outer cylinder 3 is waterjacketed at 19. Any

cylinder leading,-

suitable mechanism ma be provided for firing the char when t e piston proper 1 is in the desire angular position.

Where it is desired that the charge should be fired spontaneously by the heat generated during compression in the working space between the pistons, this may be effected by arranging that the secondary sleeve piston 2 not only follows up the piston proper 1 to insure the maintenance of compression as the piston 1 moves from the dead center to the firing position, but actually overtakes the primary piston to some extent. This accelerating movement of the sleeve piston is obtained by coupling its connecting rods up to cranks having a greater throw than that of the crank of the primary piston. Such maximum compressioncorresponding to the closest approach of the piston and the piston sleeve is arranged to take place when either the piston crank or the sleeve piston crank has moved a suitable an le past the dead center position, the movab e piston elements then inclosing the minimum compression space. The position of the sleeve piston cranks may be arranged to be on the other dead center at the moment of firing, but should the position of those cranks be slightly behind the dead center,'no back fire will result, by reason of the greater turning efiort being developed on the primary piston crank which is then at a considerable angularposition in advance of its dead center, this greater effort easily overcoming the slight back thrust which might be set up on the other crank. B a suitable disposition of the angularity o the cranks in such an arrangement, the maximum compression may be arranged to occur at any angular position of the effective crank within considerable limits, and this maximum compression is arranged to be sufficient to cause spontaneous firing of the fuel charge, thus eliminating the necessity for firing the charge by means of sparking plugs disposed in one of the movable pistons, or through ports in the side of the piston sleeve.

In order to insure that the "olume of combustible mixture pumped through the valve 10 is suiiicicnt to fill the firing space between the sleeve piston and the piston proper when at their maximum apart, the secondary sleeve piston may be provided with an enlarged head 2* and the ore of the cylinder stepped. The enlarged head portion may he detachably secured to the sleeve piston either by screwing or it may be secured in the manner of a junk ring, that is by circumferential bolts, this construction enabling the engine to be dismantled by removing the enlarged head when the body of the sleeve piston may be withdrawn downward. Or, alternatively, the lower art or member 20 of the. sleeve piston to w ich the connecting 3 correspondingly distance rods 5 are pivoted may be made detachable, the head 2 being integral with the sleeve piston, and in this arrangement the sleeve piston would be withdrawn by removing the ring element 20 to which the connecting rods are attached, the stepped sleeve piston being then withdrawn through the head of the cylinder. By forming the sleeve piston with an enlarged head and the outer fixed cylinder stepped to correspond, a greater vol ume of combustible mixture may be compressed in the space 9 and subsequently pumped into the sleeve piston, and by varying the diameter of the fixed cylinder and of the sleeve piston head the amount of com bustible mixture so pumped into the working space may be arranged to be any quantity desired. A further advantage accruing from this arrangement arises from the fact that the annular space 21 in the fixed c linder below the enlarged head of the seeve piston may be used in smaller engines to act as a pump, drawing in cool air through suitable ports 22 on the upward travel of the sleeve piston and discharging such air on the downward stroke, this pumping of cool air into and out of the fixed cylinder cooling such cylinder and the sleeve piston and consequently the inner piston proper. In large engines this annular space may be used as a primary pump, the air when drawn into the annular space by the suction action of the sleeve piston being afterward delivered under pressure on the downward stroke of the sleeve piston. Such air, at a pressure of, say, about 100 lbs. per square inch, may be delivered to a reservoir or container from which it is afterward taken by a pump and compressed up to any desired pressure and then utilized for reversing the engine, say, by having starting valves attached to each cylinder and providing means for admitting such compressed air to that cylinder of the series, the crank of which is in the correct angular position for receiving a reversing impulse on the engine.

In the case of marine engines air inlets 23 may be provided and fitted with auxiliary starting valves to admit compressed air at any desired pressure into the fixed cylinder 3, which air passing by way of the valve 10 would act on the primary piston 1 which was in a favorable angular position for starting and set up an initial turning move- 'ment on the engine crank shaft.

Engines constructed and arranged on this principle so as to fire when one crank is in an angular position in advance of the dead center would show a greater fuel economy for a given horse power by reason of the greater torque developed and owing to the reduction of direct thrust stresses, would lend themselves to a greater lightness in construction.

I claim:

1. An. internal combustion engine, comprising, a primary piston, a secondary sleeve piston having an enlarged head, an outer cylinder Within which both pistons Work and stepped to fit the enlarged sleeve piston head, a combustible mixture inlet valve in the sleeve piston, said enlarged head pumping the charge into the sleeve piston, cranks set at 135 to 145 degrees apart to which the pistons are coupled, the combustible mixture being fired between the pistons when one crank has moved 35 to 45 degrees past the dead center, compression of the combustible mixture being maintained during the movement of that crank and its piston from the dead center to the firing position by a compensating movement of the other piston.

2. An internal combustion engine, comprising, a primary piston, a secondary sleeve piston having an enlarged head, an outer cylinder within which both pistons work and stepped to fit the enlarged sleeve piston head, a combustible mixture inlet valve in the sleeve piston, said enlarged head pumping the combustible charge into the sleeve piston and also acting as a pump to circulate cooling air through the cylinder, cranks set at 135 to 145 degrees apart to which the pistons are coupled, the combustible mixture bein fired between the pistons when one cran has moved 35 to 45 degrees past'the dead center, compression of the combustible mixture being maintained during the movement of that crank and its piston from the dead center to the firing position by a compensating movement of the other piston.

In testimony whereof I afiix my signature in presence of two witnesses.

JOSEPH KNIGHT.

Witnesses A. J Dxvms, E. HmmBo'mAM. 

